A solid oxide fuel cell (SOFC) is an electrochemical device that converts chemical energy directly into electrical energy. A solid oxide regenerative fuel cell (SORFC) is an electrochemical device that converts electrical energy directly into chemical energy and subsequently reconverts chemical energy back to electrical energy. This device differs significantly from rechargeable batteries in that the chemicals are stored outside of the SORFC converter. The SORFC system has many building electrical energy storage applications that cannot be satisfied by batteries. For example, a SORFC system for building power generation is discussed in the Proceedings of the 2001 DOE Hydrogen Program Review NREL/CP-570-30535. A SORFC system which generates hydrogen in the electrolysis mode and which generates electricity in the fuel cell mode is described in Proceedings of the 2002 DOE Hydrogen Program Review NREL/CP-610-32405. This SORFC system may contain a separate electrolyzer unit which operates in the electrolysis mode and which is operatively connected to the fuel cell stack to generate hydrogen. However, these SORFC systems have certain environmental and economic drawbacks.
The SOFC and SORFC are high temperature electrochemical systems. Another high temperature electrochemical system is a molten carbonate fuel cell. Fuel cells often use hydrogen as fuel. For example, fuel cell powered vehicles would require hydrogen refueling stations for operation. However, distribution of hydrogen from centralized hydrogen producing plants to refuel vehicles is not currently economical. Furthermore, hydrogen production is fairly expensive.